Changes in dityrosine content of injured and aging blood vessels will be evaluated to determine the role of this reduced oxygen derived crosslinked peptides in matrix maturation and morphogenesis. Efforts to isolate dityrosine crosslinked peptides and possible identification of the proteins of origin will be attempted using proteolytic dissection of vascular tissue. Further characterization of renin synthesis by cultured arterial smooth muscle cells and the possible regulation of this biosynthetic activity in cell and organ culture will be pursued. These studies are directed at claryfing the role of the vasculature in the local regulation of its own tone and proliferative response to injury. Further characterization of the platelet collagen interaction particularly with the basement membrane collagens, type IV and V, which do not interact with platelets is being pursued using affinity columns and labeled platelets. These studies are designed to determine the non-thrombogenic extent of vascular basement membranes.